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.\" Copyright 2023 Oxide Computer Company
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.Dd June 2, 2023
.Dt DDI_UFM 9E
.Os
.Sh NAME
.Nm ddi_ufm ,
.Nm ddi_ufm_op_nimages ,
.Nm ddi_ufm_op_fill_image ,
.Nm ddi_ufm_op_fill_slot ,
.Nm ddi_ufm_op_getcaps
.Nd DDI upgradable firmware module entry points
.Sh SYNOPSIS
.Vt typedef struct ddi_ufm_handle ddi_ufm_handle_t
.Vt typedef struct ddi_ufm_ops ddi_ufm_ops_t
.In sys/ddi_ufm.h
.Ft int
.Fo ddi_ufm_op_getcaps
.Fa "ddi_ufm_handle_t *uhp"
.Fa "void *drv_arg"
.Fa "ddi_ufm_cap_t *caps"
.Fc
.Ft int
.Fo ddi_ufm_op_nimages
.Fa "ddi_ufm_handle_t *uhp"
.Fa "void *drv_arg"
.Fa "uint_t *nimgp"
.Fc
.Ft int
.Fo ddi_ufm_op_fill_image
.Fa "ddi_ufm_handle_t *uhp"
.Fa "void *drv_arg"
.Fa "uint_t imgno"
.Fa "ddi_ufm_image_t *imgp"
.Fc
.Ft int
.Fo ddi_ufm_op_fill_slot
.Fa "ddi_ufm_handle_t *uhp"
.Fa "void *drv_arg"
.Fa "uint_t imgno"
.Fa "uint_t slotno"
.Fa "ddi_ufm_slot_t *slotp"
.Fc
.Ft int
.Fo ddi_ufm_op_readimg
.Fa "ddi_ufm_handle_t *uhp"
.Fa "void *drv_arg"
.Fa "uint_t imgno"
.Fa "uint_t slotno"
.Fa "uint64_t len"
.Fa "uint64_t offset"
.Fa "void *buf"
.Fa "uint64_t *nreadp"
.Fc
.Sh INTERFACE LEVEL
.Sy Evolving - This interface is evolving still in illumos. API and ABI stability is not guaranteed.
.Sh PARAMETERS
.Bl -tag -width Fa
.It Fa uhp
A handle corresponding to the device's UFM handle.
This is the same value as returned in
.Xr ddi_ufm_init 9F .
.It Fa drv_arg
This is a private value that the driver passed in when calling
.Xr ddi_ufm_init 9F .
.It Fa nimgp
A pointer that the driver should set with a number of images.
.It Fa imgno
An integer indicating which image information is being requested for.
.It Fa imgp
An opaque pointer that represents a UFM image.
.It Fa slotno
An integer indicating which slot information is being requested for.
.It Fa slotp
An opaque pointer that represents a UFM slot.
.It Fa len
Indicates the number of bytes from a firmware payload that are desired.
.It Fa offset
Indicates an offset in a firmware payload to start reading from.
.It Fa buf
A buffer to place raw firmware data from the device into.
.It Fa nreadp
A pointer whose value should be updated with the number of bytes
actually read from the image.
.El
.Sh DESCRIPTION
Upgradable firmware modules (UFM) are a potential component of many
devices.
These interfaces aim to provide a simple series of callbacks
for a device driver to implement such that it is easy to report
information and in the future, manipulate firmware modules.
.Ss UFM Background
UFMs come in different flavors and styles that vary from device to
device.
.Qq Firmware
generally refers to some form of software that runs on a device and is often
packaged up as a binary payload.
However, many things that aren't always called
.Qq firmware ,
such as EEPROM images, CPU microcode, flash based configuration, and more, are
all just as important here.
Take for example a hard drive.
While it is a field replaceable unit (FRU), it also contains some amount
of firmware that manages the drive which can be updated independently of
replacing the drive.
.Pp
The motherboard often has a UFM in the form of the BIOS or UEFI.
The Lights Out Management controller on a system has a UFM, which is usually
the entire system image.
CPUs also have a UFM in the form of microcode.
.Pp
An important property of a UFM is that it is a persistent part of the device
itself.
For example, many WiFi device drivers are required to send a binary blob of
firmware to the device after every reset.
Because these images are not persistent parts of the device and must be upgraded
by either changing the device driver or related system files, we do not consider
these UFMs.
.Pp
There are also devices that have firmware which is a part of the
device, but may not be upgradable from the running OS.
This may be because the vendor doesn't have tooling to upgrade the image or
because the firmware image itself cannot be upgraded in the field at all.
For example, a YubiKey has a firmware image that's burned into it in the
factory, but there is no way to change the firmware on it short of
replacing the device in its entirety.
However, because these images are a permanent and persistent part of the device,
we also consider them a UFM.
.Ss Images and Slots
A device that supports UFMs is made up of one or more distinct firmware
images.
Each image has its own unique purpose.
For example, a motherboard may have both a BIOS and a CPLD image, each of which
has independent firmware revisions.
.Pp
A given image may have a number of slots.
A slot represents a particular version of the image.
Only one slot is considered the
.Em active
slot.
It represents the currently running version of the image.
Devices support multiple slots so that an image can be downloaded to an inactive
slot without risking damage to the active slot.
This ensures that a power-loss or failure halfway through writing to a slot
doesn't leave the device with corrupted firmware.
.Pp
The various entry points are designed such that all a driver has to do
is provide information about the image and its slots to the kernel, it
does not have to wrangle with how that is marshalled to users and the
appearance of those structures.
.Ss Registering with the UFM Subsystem
During a device driver's
.Xr attach 9E
entry point, a device driver should register with the UFM subsystem by
filling out a UFM operations vector and then calling
.Xr ddi_ufm_init 9F .
The driver may pass in a value, usually a pointer to its soft state
pointer, which it will then receive when its subsequent entry points are
called.
.Pp
Once the driver has finished initializing, it must call
.Xr ddi_ufm_update 9F
to indicate that the driver is in a state where it's ready to receive
calls to the entry points.
.Pp
The various UFM entry points may be called from an arbitrary kernel
context.
However, they will only ever be called from a single thread at
a given time.
.Ss UFM operations vector
The UFM operations vector is a structure that has the following members:
.Bd -literal -offset indent
typedef struct ddi_ufm_ops {
	int (*ddi_ufm_op_nimages)(ddi_ufm_handle_t *uhp, void *drv_arg,
	    uint_t *nimgp);
	int (*ddi_ufm_op_fill_image)(ddi_ufm_handle_t *uhp, void *drv_arg,
            uint_t imgno, ddi_ufm_image_t *imgp);
	int (*ddi_ufm_op_fill_slot)(ddi_ufm_handle_t *uhp, void *drv_arg,
            int imgno, ddi_ufm_image_t *img, uint_t slotno,
	    ddi_ufm_slot_t *slotp);
	int (*ddi_ufm_op_getcaps)(ddi_ufm_handle_t *uhp, void *drv_arg,
	    ddi_ufm_cap_t *caps);
	int (*ddi_ufm_op_readimg)(ddi_ufm_handle_t *uhp, void *drv_arg,
	    uint_t imgno, uint_t slotno, uint64_t len, uint64_t offset,
	    void *buf, uint64_t *nreadp);
} ddi_ufm_ops_t;
.Ed
.Pp
The
.Fn ddi_ufm_op_nimages
and
.Fn ddi_ufm_op_readimg
entry points are optional.
If a device only has a single image, then there is no requirement to implement
the
.Fn ddi_ufm_op_nimages
entry point and it may be set to
.Dv NULL .
The system will assume that there is only a single image.
.Pp
Slots and images are numbered starting at zero.
If a driver indicates support for multiple images, through the
.Fn ddi_ufm_op_nimages
entry point, or slots, by using the
.Xr ddi_ufm_image_set_nslots 9F
function in the
.Fn ddi_fum_op_fill_image
callback then the images
or slots will be numbered sequentially going from 0 to the number of images or
slots minus one.
These values will be passed to the various entry points to indicate which image
and slot the system is interested in.
It is up to the driver to maintain a consistent view of the images and slots
for a given UFM.
.Ss Fn ddi_ufm_op_nimages
The
.Fn ddi_ufm_op_nimages
entry point is an optional entry point that answers the question of how
many different, distinct firmware images are present on the device.
Once the driver determines how many are present, it should set the value in
.Fa nimgp
to the determined value.
.Pp
It is legal for a device to pass in zero for this value, which indicates
that there are none present.
.Pp
Upon successful completion, the driver should return
.Sy 0 .
Otherwise, the driver should return the appropriate error number.
For a full list of error numbers, see
.Xr Intro 2 .
Common values are:
.Bl -tag -width Er -offset width
.It Er EIO
An error occurred while communicating with the device to determine the
number of firmware images.
.El
.Ss Fn ddi_ufm_op_fill_image
The
.Fn ddi_ufm_op_fill_image
entry point is used to fill in information about a given image.
The value in
.Fa imgno
is used to indicate which image the system is asking to fill
information about.
If the driver does not recognize the image ID in
.Fa imgno
then it should return an error.
.Pp
The
.Ft ddi_ufm_image_t
structure passed in
.Fa imgp
is opaque.
To fill in information about the image, the driver should call the functions
described in
.Xr ddi_ufm_image 9F .
.Pp
The driver must call the
.Xr ddi_ufm_image_set_desc 9F
function to set a description of the image which indicates its purpose.
This should be a human-readable string.
In addition, the driver must call the
.Xr ddi_ufm_image_set_nslots 9F
function to indicate the number of slots that the device supports for
that particular firmware image.
The driver may also set any ancillary data that it deems may be useful with the
.Xr ddi_ufm_image_set_misc 9F function.
This function takes an nvlist, allowing the driver to set arbitrary keys and values.
.Pp
Once the driver has finished setting all of the information about the
image then the driver should return
.Sy 0 .
Otherwise, the driver should return the appropriate error number.
For a full list of error numbers, see
.Xr Intro 2 .
Common values are:
.Bl -tag -width Er -offset width
.It Er EINVAL
The image indicated by
.Fa imgno
is unknown.
.It Er EIO
An error occurred talking to the device while trying to fill out
firmware image information.
.It Er ENOMEM
The driver was unable to allocate memory while filling out image
information.
.El
.Ss Fn ddi_ufm_op_fill_slot
The
.Fn ddi_ufm_op_fill_slot
function is used to fill in information about a specific slot for a
specific image.
The value in
.Fa imgno
indicates the image the system wants slot information for and the value
in
.Fa slotno
indicates which slot of that image the system is interested in.
If the device driver does not recognize the value in either or
.Fa imgno
or
.Fa slotno ,
then it should return an error.
.Pp
The
.Ft ddi_ufm_slot_t
structure passed in
.Fa slotp
is opaque.
To fill in information about the image the driver should call the functions
described in
.Xr ddi_ufm_slot 9F .
.Pp
The driver should call the
.Xr ddi_ufm_slot_set_version 9F
function to indicate the version of the UFM.
The version is a device-specific character string.
It should contain the current version of the UFM as a human can understand it
and it should try to match the format used by device vendor.
.Pp
The
.Xr ddi_ufm_slot_set_attrs 9F
function should be used to set the attributes of the UFM slot.
These attributes include the following enumeration values:
.Bl -tag -width Dv
.It Dv DDI_UFM_ATTR_READABLE
The
.Dv DDI_UFM_ATTR_READABLE
attribute indicates that the firmware image in the specified slot
may be read, even if the device driver does not currently support such
functionality.
.It Dv DDI_UFM_ATTR_WRITEABLE
The
.Dv DDI_UFM_ATTR_WRITEABLE
attribute indicates that the firmware image in the specified slot
may be updated, even if the driver does not currently support such
functionality.
.It Dv DDI_UFM_ATTR_ACTIVE
The
.Dv DDI_UFM_ATTR_ACTIVE
attribute indicates that the firmware image in the specified slot
is the active
.Pq i.e. currently running
firmware.
Only one slot should be marked active.
.It Dv DDI_UFM_ATTR_EMPTY
The
.Dv DDI_UFM_ATTR_EMPTY
attribute indicates that the specified slot does not currently contain
any firmware image.
.El
.Pp
If the driver supports the
.Fn ddi_ufm_op_readimg
entry point, then the driver should attempt to determine the size in
bytes of the image in the slot and indicate that by calling the
.Xr ddi_ufm_slot_set_imgsize 9F
function.
.Pp
Finally, if there are any device-specific key-value pairs that form
useful, ancillary data, then the driver should assemble an nvlist and
pass it to the
.Xr ddi_ufm_slot_set_misc 9F
function.
.Pp
Once the driver has finished setting all of the information about the
slot then the driver should return
.Sy 0 .
Otherwise, the driver should return the appropriate error number.
For a full list of error numbers, see
.Xr Intro 2 .
Common values are:
.Bl -tag -width Er -offset width
.It Er EINVAL
The image or slot indicated by
.Fa imgno
and
.Fa slotno
is unknown.
.It Er EIO
An error occurred talking to the device while trying to fill out
firmware slot information.
.It Er ENOMEM
The driver was unable to allocate memory while filling out slot
information.
.El
.Ss Fn ddi_ufm_op_getcaps
The
.Fn ddi_ufm_op_getcaps
function is used to indicate which DDI UFM capabilities are supported by this
driver instance.
Currently, all UFM-capable drivers are required to implement the
.Dv DDI_UFM_CAP_REPORT
capability.
The following capabilities are supported and the drivers should return a
bitwise-inclusive-OR of the following values:
.Bl -tag -width Dv -offset width
.It Dv DDI_UFM_CAP_REPORT
Indicates that the driver is capable of reporting UFM information and
implements the
.Fn ddi_ufm_op_fill_slot
and
.Fn ddi_ufm_op_fill_image
entry points.
It also indicates, that it optionally implements
.Fn ddi_ufm_op_nimages
entry point.
.It Dv DDI_UFM_CAP_READIMG
Indicates that the driver is capable of reading a binary firmware
payload off of a device.
.El
.Pp
The driver should indicate the supported capabilities by setting the value in
the
.Ft caps
parameter.
Once the driver has populated
.Ft caps
with an appropriate value, then the driver should return
.Sy 0 .
Otherwise, the driver should return the appropriate error number.
For a full list of error numbers, see
.Xr Intro 2 .
Common values are:
.Bl -tag -width Er -offset width
.It Er EIO
An error occurred talking to the device while trying to discover firmware
capabilities.
.It Er ENOMEM
The driver was unable to allocate memory.
.El
.Ss Fn ddi_ufm_op_readimg
The
.Fn ddi_ufm_op_readimg
is an optional entry point that allows the system to read a binary
firmware payload from the device.
The driver should read the firmware payload indicated by both
.Fa imgno
and
.Fa slotno .
The driver should check to make sure that the region requested, starting
at
.Fa offset
bytes into the image
and
.Fa len
bytes long is valid for the image and if not, return the error
.Er EINVAL .
Data from the device should be copied into
.Fa buf
and the number of bytes successfully read should be placed into
.Fa nreadp .
.Pp
Upon successfully reading this data, the driver should return
.Sy 0 .
Otherwise the driver should return the appropriate error number.
For a full list of error numbers, see
.Xr Intro 2 .
Common values are:
.Bl -tag -width Er -offset width
.It Er EINVAL
The image or slot indicate by
.Fa imgno
and
.Fa slotno
is unknown.
The combination of
.Fa offset
and
.Fa len
would overflow or read from a region of the image which is not valid.
The device currently has an alignment restriction and the requested
offset and length do not honor that.
.It Er EIO
An error occurred while communicating with the device to read the
firmware image.
.It Er ENOTSUP
The driver does not support reading a firmware payload on this device or
from a particular image and slot.
.El
.Ss Caching and Updates
The system will fetch firmware and slot information on an as-needed
basis.
Once it obtains some information, it may end up caching this information on
behalf of the driver.
Whenever the driver believes that something could have changed then the driver
must call
.Xr ddi_ufm_update 9F .
The driver does not need to know for certain that something has changed.
For example, after a device reset or firmware upgrade, the driver doesn't need
to check if the firmware revision changed at all, it can simply call
.Xr ddi_ufm_update 9F .
.Ss Locking
All UFM operations on a single UFM handle will always be run serially.
However, the device driver may still need to apply adequate locking to
its structure members as other entry points may be called on the device in
parallel, which could access the same data structures and try to communicate
with the device.
.Ss Unregistering from the UFM subsystem
When a device driver is detached, it should unregister from the UFM
subsystem.
To do so, the driver should call
.Xr ddi_ufm_fini 9F .
By the time this function returns, the driver is guaranteed that no UFM
entry points will be called.
However, if there are outstanding UFM related activity, the function will
block until it is terminated.
.Ss ioctl Interface
Userland consumers can access UFM information via a set of ioctls that are
implemented by the
.Xr ufm 4D
driver.
.Sh CONTEXT
The various UFM entry points that a device driver must implement will
always be called from
.Sy kernel
context.
.Sh SEE ALSO
.Xr Intro 2 ,
.Xr ufm 4D ,
.Xr attach 9E ,
.Xr ddi_ufm_fini 9F ,
.Xr ddi_ufm_image 9F ,
.Xr ddi_ufm_image_set_desc 9F ,
.Xr ddi_ufm_image_set_misc 9F ,
.Xr ddi_ufm_image_set_nslots 9F ,
.Xr ddi_ufm_init 9F ,
.Xr ddi_ufm_slot 9F ,
.Xr ddi_ufm_slot_set_attrs 9F ,
.Xr ddi_ufm_slot_set_misc 9F ,
.Xr ddi_ufm_slot_set_version 9F ,
.Xr ddi_ufm_update 9F
